Dental epoxides

ABSTRACT

A PACK SUITABLE FOR THE PRODUCTION OF A CURED POLYEPOXIDE RESIN COMPOSITION, WHICH COMPRISING A POLYEPOXIDE RESIN, A CURING AGENT COMPRISING A COMPLEX OF A FRIEDEL-CRAFTS&#39;&#39; CATALYST AND AN AQUEOUS STRONG NON-CARBOXYLIC ACID OR AQUEOUS FLUOACID, AND MEANS TO PREVENT PREMATURE REACTION BETWEEN THE RESIN AND THE CURING AGENT.

3,799,905 Patented Mar. 2c, 1974 United S at Paten Qfic 9 3,799,905 DENTAL EPOXIDES Winchester, "and Brian Maurice WilliamHollowtty,

' 'Edward Causton, Basingstoke, Englandyasslgnors' to al Research England Development Corporation, London, N Drawing. Filed Se t. 22, 1971, Ser. No. 182,843

Clai s priority, appl ti n Gr B i ai Sept-2.4, 1.9. .0,

45,609/70; Apr, so, 1971, 12,542/71 I 111:. CI. c0s -51/o4 U.s. ct. zen-37,1211.

-ABS'I- RA 'CT OF THE DISCLOSURE A-pack suitable for .the production of a cured polypezsi tss n s q t h ch comprises a PQ YsPP ide resin, a curing agent comprising a complex of a Friedel-Craft's catalyst and an aqueous strongnon-carboxylic acid or aqueous fluoacid, and means to prevent premature reaction between the resin and the curing agent.

. This invention relatesto polyepoxide resins, and is moreparticularly concerned with polyepoxide resin com positions adapted for use in the field of dentistry.

Polyepoxide resins are available as liquids which can 11 Claims 7 organic acid. such as for example nitric acid, hydrochloric acid, or an organic acid for example a sulphonic acid such as p-toluene sulphonic acid and preferably benzene m-di- 'sulphonic acid. The term strong acid in this specification includes acids having a dissociation constant (K value) of not less than 5x10- and preferably not less than 1x10- The fluoacid is preferably an acid of fluorine having a dissociation constant (K value) of less than 5 l0- and is most preferably hydrofluoric acid. Concentrated solutions of the acids containing at least be cured. at ambient temperature with negligible shrinkv/o of the acid are preferred. Mixtures of the acids may beuscd.

The complex is preferably formed by adding the Friedel Crafts catalyst to the aqueous strong non-carboxylic acid with continual stirring. Preferably the proportion by weight of the catalyst to the acid solution is from 1:2 to 1:4, such as for example 1:3.

The' pack may be a two part pack in which the ratio of curing agent to polyepoxide resin in the two parts is preferably from 0.02 to 0.2 millilitre per gram so that discloses .a stable, complex of a,Friedel-Crafts-catalyst l);

the susceptibility" of" the c a'talysts to hydrolysis which if rendersithecatalyst inactive.

wardi "tq.tlzqpr ssntis sntisln thesis pr vided a eomplexed FriedelgCrafts catalyst, suitable for use the curingjof'polyepoxide resins, having improved prop- I cities} in this respect.

The present invention provides a pac suitable for the;

production of a cured polyepoxide resin composition,

is m t s a P YP r s a e t n ageilf i prisijngla complex are Friedel-Craftsfcatalyst and an aqueous strong non carboxyhc acid or. aqueousfluoacid andmeans ;to prevent premature reaction between the resinandthe curing agentfi H611 ef .ja"c'iired xitle resin "'cbihposition, which h P T f fi m rq ctw a p y p sr j f ple by reference to epoxide composition produced acand ;a curing agent comprising. a'.complex ofa Friedel- Crafts catalyst and anaqueous strong n'oncarboxylic acid when the entire contents of the two parts are mixed to. gether a rapidly hardening polyepoxide resin composition is obtained; In another embodiment the pack may contain the polyepox'ide resin and the curing agent in separate capsulcs,'the total amount of polyepoxide resin in the pack and the total amount of curing agent in the pack being in the desired ratio. In a further embodiment both components may be encapsulated in the same capsule, in the desired ratio, provided that steps are taken to prevent premature reaction, for example, by the provision of a membrane between the components which may be ruptured before use.

--Where the polyepoxide resin compositions are to be used in restorative dentistry it is usually desirable to reduce the thermal co-efiicient of expansion of the composition and to render I it opaque. This may conveniently be achieved by including-in the composition up to about 4 times the weight of resin, and preferably 1.5 to 2.5, times the weight'o'f resin, of an inert mineral in powder form. The inert mineral may be premixed with one or both of the components priornto the curing step but-preferably it 'ispremixed withthe resin. The inert mine ral should be chosen so that the final composition resembles as closely as possible a natural tooth in appearance. Suitable inert minerals include silica and quartz, which preferably have a particle size of less than mesh,-such as forv example 300 mesh. When using the invention for the production of dental restorations and prostheses, the

,. polyepoxide resin preblended with the inert mineral is mixed with the curing a'gent to form a putty,,and then 'l 'intr'odiic ed' into, for example, a dental cavity, formed to The mvevmlon also s sd s r 9s t e roducvention include particularly those derived from dihydric positions in moist shape, and allowed to cure. The nature of the present invention is hereafter further explained by way of examenvironments.

-. EXAMPLE 1 Cnrable epoxide compositions are made by mixing a cording-to the invention and to the curing of these com phenols; these having at-least two epoxide' groups"per "polyepoxide're'sin' mix with each of a series of complexes time. The gel time is considered as the time interval during which the resin-complex mix remains a putty and the cure time is considered the interval after which the surface can no longer be indented or deformed by hand pressure with a spatula blade. The following gel and cure times are obtained.

To illustrate the cureof compositions in moist environments the resin mix and complex components. ofjc'ompositions based on SnCL, and SbCl are first mixed. in air for 30 sees. and then put in a humidity oven at 100% TABLE 1 Halide SbCl; SnCli BFs-ZHlO Gel Cure Gel Cure Gel Cure Strong non-earboxylic acid time time time time time time HCl (35% solution) 8'0 2'10" 5'45" 3'30" 60" HNOs (70% solution)- 1'20" 10'0" 1'20" 1'35" 0'25" 0'25" Para-toluene sulphonic acid (60%). 1'40" 3'30 '20" 1'15" 1'15" Benzene m-di-sulphonic acid (33%) 1'15" 11'0" 1'30" 2'15" 2'0" 2'5" epoxide resin mix, in each of the BF complexed compositions is a mix of MY 750 resintsupplied by 'CIBA (ARL)"L'td. and believed to be a low molecular weight condensation product of diphenylolpropane with epichlorohyd'rin) with 300 mesh acid-washed silica powder. A suitable silica powder for use with the resin is Lockaline sand. The sand is thoroughly acid-washed (with aq. HNO until the washings show no discoloration. The washed and, subsequently, dried sand is then silane treated to improve adhesion to the resin: a silane solution e.g. 2% aqueous glycidoxy propyltrimethoxy silane. is mixed with the sand to form a slurry, the slurry is oven-dried and the treated sand sieved to recover the 300 mesh fraction. The Lockaline sand is used with the proportions 1.50:1 sand to resin by weight.

The halides are complexed by slowly adding each halide to an aqueous solution of each complexing acid the addition being effected at room temperature with continual stirring; both SbCl and SnCl being liquids at ambient temperature and BF added as BF .2H O, also a liquid at ambient temperature. The halides and the BE, dihydrate are aded to the acid solutions in proportions of 1:3 by wt. The acid solutions are as follows: 35 W0 H01, 70 v/o HNO 60 v/o para-toluene sulphonic acid and 33 v/o benzene-m-disulphom'c acid. The I complexed halide is added to the resin mix in each composition, in amounts of 0.02 ml. of complex to 1.0 gm. of mix.

Measurements are made of gel time and cure time initially in a dry environment i.e., ambient humidity to establish the catalytic activity of each complex and to show that theprepared compositions cure in a reasonable RH (relative humidity) and 37 C. Thefollowing cure times-Table 2are obtained, compared with cure timesat ambient humidity.

The table also includes post-cure hardness values of the compositions recorded after leaving for 4 hrs. in air and 4 hrs. in the oven: the hardness values record the force applied to a dia. steel ball to form an indentation 0.010 deep.

TABLE 2 Hardness Hardness Cure at air cure moist cure Cure 100% RH plus 4 plus 4 hrs. Complex in air at 37 0. hrs., lbf. in oven, lbf

SnCl plus 33 v/o benzene sulphonic acid.... 2'15" 47. 5 57. 5

Such plus 35 v/o HCL- 5'45" 16' 15" 10. 2 62. 3 SnCl; plus 70 v o HNOQ. 1'35" 1'25" 45. 0 59. 0 SbCla plus 70 v/o HNOg. 10'0" 11'0" 49. 0 58. 0 819015 plus 60 v/o toluone sulphonic acid--- 3'30" 1'10" 41. 5 56. 5

In a more stringent evaluation, the curability of compositions in moistconditions isassessed by making additions of up to 10 w/o water to the resin mix, based on the resin content of the mixture, the water being added TABLE 3.-EFFECT OF WATER ON CURE TIMES v v The results of Table 3 show, in particular, that with higher amounts of the Such/benzene sulphonic acid complex, within the stated range, a reasonable cure time can, be achieved with up to w/o water in the resin mix. For comparable cure times the water tolerance of theSbClg/ toluene sulphonic acid complex, used in controlled amounts, is not much'more'than 1%. However it has to be realized that the blending in of even 1% water with the resin mix represents an exceptionally severe moist environment. Table 4 shows that with higher amounts ;of the BF -2H O/benzene sulphonic acid complex, very reasonable cure times can be achieved with up to 10 w/o water in the resin mix.

The importance of epoxide compositions according to theinvention. resides in the fact that a dental cavity cannot be kept completely'dry prior to insertion of a dental filling material therein because of 'the' moisture of the mouth and the continuous exudation "of moisturefrom tubules infthe dentine. v I J if The" resistance of cured compositions to" sustained exposure to moisture, such as are found in the mouth, is evaluated by hardness and compressive strength measurements. Specimens are stored at 40 C. and 100% relative humidity, am of water depositing on the specimen surfaces, for periods of 14, 28, 100 and 133 days. The results together with the values at cure are shown 'in Table 5. Hardness is determined by measuring the load required to indent the surface of a flat bar (/a" thick is i" wide) to a depth of 0.01 in. with a ,4 die. steel ball. Compressive strength is the strength at failure of cylinders (16 long x A" dia.) using a testing machine crosshead speed of 0.02 in./min.

2 flfQ Curable, poly epoxide compositions are made by mixmg a pro-prepared polyepoxide resin mix with an HF iiiiii'iple'xed' lialideITho halide is ehesenrfem SIS Q15, 'SnCl; 'iiCl SiCl FeCl and AlCl' The complexed-halide is added tothe resin in each composition, inamounts' of 0.02'ml'xot complex to 1.0 gm; of mix. The polyepoxide resin mixuin each composition-is a mix of-'MY 750resin (supplied by 0113A (ARL) Ltd.) with 300 mesh acid. washed "silica powder," the-mix consisting of 0.4 g'mJ- of resinfor e'ach'0.6 'gnnof silicapowder; i The halides are co plexed by slowly addihg-e'a'cliyhalide to an'aqueous vol. percent'solution of HF the addition being etfect'edat room temperature" with continual stirring: *SbClg; SnCl -TiCl, and SiCl, are liquids'at ambient temperature and FeCl, a'nd'AlCl, are solids. halidesareaddedto' the acid solution in proportions or Measurements were made of gel time and cure 'timein Q aimoist' envir'onment and, for comparison, in a dry environment i.e.' ambient humidity as described in Exam pie-PL;

lThe'followrng 'gel and cure times are obtained for the HF-compiexed alides. i I 7 Halide Gel time Cure time I Gel times cure time abet. 1' o" 1" s" A1011. 4 hrs FeOh. 4 hrs TABLE 5.--HARDNESS, COMPRESSIVE STRENGTHS AND HUMID AGING Hardness, lbf. at RH aging alter- Compressive strength, lbL/inJ at 100% RH aging after- Metal halide Complexing acid 0 14 days 28 days 100 days 0 14 days 28 days 133 days 81101; Benzene m di-sulphonic acid 33 0 33. 7 55.0 49. 3 45. 0 13,335 16, 060 14, 669 9, 753 $1101 dn SnCl4 47. 5 45. 0 42.3 43. 8 14, 250 15, 14, 678 10, 584 bC1 10. 2 33.5 v 32.0 31. 8 10,535 11, 14,316 8,64% SnCh- HNO; (70%) 49-0 60.5 58.8 49.5 15.240 16,920 17, 281 11, 112 SnCl p Toluene sulphomc ac d (33%)..- 45. 0 49. 0 43. 5 46. 0 14, 585 15, 235 15, 209 12, 043 Such. p Toluene sulphonic ac d (66%)..- 41. 7 43. 5 40. 0 43. 5, 10, 060 14, 960 020 12, 690 SbCh.. p Toluene sulphomc acid (60%)-.- 36. 8 48. 0 44. 5 42. 5: 10, 14,080 12, 9, 981 zmo Benzene m di-sulphonic acid 41. 5 5a 0 e1. 5 51. 0 12, 505 16,895 ,318 14, 629 (33%) 59. 7 49.5 43.5 19,561 18,856 16,738

Hardness measurements with 54; die. steel ball (indented 0.01").

The results show that hardness and compressive strength 50 It w ll be apparent that HF-complexed SbCl; and SnCl.

values are substantially unaffected by exposure to moisture.

Apart from the tolerance to moisture of the epoxide compositions when curing and when cured the significance of water as a diluent in the aqueous acid solutions has to be considered. Diluent water affects the reactivity of complexes as shown in the following table (Table 6) which shows, by way of example, SnCl and SbCl5 complexed with toluene sulphonic acid. Increasing the dilution re suits in increased cure times.

provide relatively fast curing compositions: the curing time for S nCl in particular, indicates the utility of this complex in dental work.

Measurements were also made of the hardness of dry air cured and moist-cured compositions.

For the moist-cured compositions the resin mix and complexfwere first mixed in air for 30 secs. and then put in a humidity oven at 100% RH and 37 C. to cure:

.160 after curing the compositions were retained in the oven TABLE 6.EFFECT 0F CONCENTRATION OF COMPLEXING ACID Weight ratio 01 components G Cure Complexes produced according to the invention do not fume in air, as do the metal halides from which they are formed, and they can be stored without visible change for at least 3 months.

for 4 his. As the hardness figures following show HF-complexed SbCl and SnCl. compositions are substantially 5 immune to the presence of moisture.

Hardness moist cure Hardness air cure plus 4 hrs. in humid- The hardness values record the force applied to a & dia. steel ball to form-an indentation 0.010" deep.

We claim: 9

:1. A process-for the spontaneous production of a mass of resin which cures rapidly in a moist environment but which remains plastic long enough to be shaped during use in a restorative dentistry which comprisesintimately mixing a polyepoxide with a curing agent, said curing agent comprising a complex of a Friedel-Crafts catalyst and an aqueous strong non-carboxylic acid having a dissociation'constant of not less than X or hydrofluoric acid, and curing said polyepoxide with said curing agent in said moist environment.

2. A process according to claim 1 in which the poly epoxide is derived from a dihydrie phenol, and has not more hydroxyl groups per molecule than epoxide groups.

3. A process according to claim 1 in which the polyepoxide is a low molecular weight condensation product of diphenylolpropane with epichlorohydrin.

4. A process according to claim 1 in which the Friedel- Crafts catalyst is a halide of aluminium, boron, antimony, titanium, silicon, iron or tin.

5. A process according to claim 1 in whichthe. Friedel- Crafts catalyst is BF SbCl TiCl SiCl FeCl AlCl or SnCl 6. A process according to claim 1 in which the strong non-carboxylic acid is nitric acid, hydrochloric acid or a sulphonic acid.

7. A process according to claim 1, in which the curing agent is-a complex of said Friedel-Crafts catalyst and hydrofluoric acid. a a v I 8. A process according to claim 1 in which the ratio of curing agent to polyepoxide is from 0.02 to 0.2 millilitre per gram.

9. A process according to claim 1 in which there is pre-mixed with the resin an inert mineral in powder form.

10. A process according to claim 9, in which the inert mineral is silica.

11.v A process according to *claim 9 in which the inert mineral has a particle size of less than mesh.

References Cited UNITED STATES PATENTS 3,629,163 12/1971 No1ken 260--2 EC X 2,824,083 2/1958 Parry et a1. 26047 EC 3,503,128 3/1970 Boyd et a1 260--37 EP Xv 3,396,117 8/1968 Schuetze 26( 37 EP X 2,436,238 2/ 1948 Wadley et al 252-433 X 2,810,774 10/ 1957 Serniuk 252-433 X OTHER REFERENCES Kirk et al.: Encyclopedia of Chemical Technology; Interscience Encyclopedia Inc.; 1951; vol. 6, pp. 680 and 683; Sci. Lib., TF9 E68.

'LEWIS T. JACOBS, Primary Examiner US. Cl. X.R. 260-2 EC, 47 EC 

